JP2010224032A - Fixing unit and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing unit, etc., in which warming up time is hardly made long even when a member is installed for dispersing heat generated from a heat generating body. <P>SOLUTION: The fixing unit 60 is provided with: a fixing belt 61 having a conductive layer for fixing toner to recording material by having the conductive layer heated by electromagnetic induction; an IH heater 80 for generating an alternating magnetic field which intersects with the conductive layer of the fixing belt 61; a temperature sensitive magnetic member 64 which is arranged in contact with an inner peripheral surface of the fixing belt 61 and forms a magnetic path for the alternating magnetic field that is generated in an IH heater 80 as well as conducting heat to the fixing belt 61 by being heated by electromagnetic induction; and an induction member 66 which is arranged in contact with the inner periphery surface of the temperature sensitive magnetic member 64 and carrying out induction of a line of magnetic force that has passed through this temperature sensitive magnetic member 64 as well as dispersing the heat generated at the temperature sensitive magnetic member 64. In this case, the fixing unit 60 is characterized by having a concavo-convex structure on at least one of the inner peripheral surface of the temperature sensitive magnetic member 64 and an outer circumferential surface of the induction member 66. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing device and an image forming apparatus.

As a fixing device mounted on an image forming apparatus such as a copying machine or a printer using an electrophotographic system, an apparatus using an electromagnetic induction heating system is known.
For example, Patent Document 1 is provided with a heat generation control member that includes a temperature-sensitive magnetic metal material having a Curie point and is disposed to face a magnetic field generator via a fixing belt having a heat generation layer. There is described a fixing device that controls the heat generation of the heat generating layer by utilizing the magnetism and non-magnetization at the Curie point of the temperature-sensitive magnetic metal material constituting the control member.
Patent Document 2 discloses a heating element that generates heat by the action of a magnetic field on the inner peripheral side of the fixing belt, and is opposed to the magnetic field generator via the fixing belt and is in contact with the inner peripheral surface of the fixing belt. A fixing device is described in which a heating element is provided and the heating element has a thickness exceeding the skin depth and includes a magnetic metal material.

JP 2008-152247 A JP 2008-129517 A

Here, in general, the fixing member heated by the electromagnetic induction coil is formed of a belt member having a small heat capacity, so that the time (warm-up time) for raising the fixing member to a fixable temperature is shortened. However, in addition to the heat generated by the fixing member, in the case of a fixing device that heats the fixing member by providing another heating element together, the heat generated from the heating element is diffused to make the temperature distribution of the fixing member uniform. There may be a case where a member is provided. At this time, since the heat flows out to the member that diffuses this heat, the warm-up time may become long.
SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device or the like in which the warm-up time is unlikely to be long even if a member for diffusing heat generated from a heating element is provided.

  According to the first aspect of the present invention, there is provided a fixing member that has a conductive layer, the toner is fixed to the recording material by electromagnetically heating the conductive layer, and an alternating magnetic field that intersects the conductive layer of the fixing member. A magnetic field generating member to be generated and an inner peripheral surface of the fixing member are arranged in contact with each other to form a magnetic path of an alternating magnetic field generated by the magnetic field generating member and to be heated by electromagnetic induction to the fixing member. A magnetic path forming member that conducts heat and disposed in contact with the inner peripheral surface of the magnetic path forming member, induces a magnetic field line that has passed through the magnetic path forming member, and generates heat in the magnetic path forming member And a guide member for diffusing the guide member, and having a concavo-convex structure on at least one of an inner peripheral surface of the magnetic path forming member and an outer peripheral surface of the guide member.

According to a second aspect of the present invention, in the fixing device according to the first aspect, the concavo-convex structure is formed in a groove shape or a ridge shape arranged substantially parallel to each other.
The invention according to claim 3 is characterized in that the concavo-convex structure is formed by a convex portion or a concave portion having at least one shape selected from a hemispherical shape, a cylindrical shape, a pyramid shape, and a spindle shape. The fixing device according to Item 1.
The invention according to claim 4 is characterized in that the concavo-convex structure is formed such that the correspondence between the temperature of the fixing member and the temperature of the magnetic path forming member is maintained. The fixing device.
The invention according to claim 5 is the fixing device according to claim 1, wherein the heat diffusion member is made of a member having a higher thermal conductivity than the magnetic path forming member as a material.

According to a sixth aspect of the present invention, there is provided a toner image forming unit that forms a toner image, a transfer unit that transfers the toner image formed by the toner image forming unit onto a recording material, and a toner image that is transferred onto the recording material. A fixing member for fixing the toner image to the recording material, the fixing unit having a conductive layer, and fixing the toner to the recording material by electromagnetically heating the conductive layer. A magnetic field generating member that generates an alternating magnetic field that intersects the conductive layer of the fixing member, and a magnetic path of the alternating magnetic field generated by the magnetic field generating member that is disposed in contact with the inner peripheral surface of the fixing member. A magnetic path forming member that conducts heat to the fixing member by being electromagnetically heated while being formed; and
An induction member that is arranged in line contact or point contact with the inner peripheral surface of the magnetic path forming member and that induces magnetic lines of force that have passed through the magnetic path forming member and diffuses heat generated in the magnetic path forming member; And an image forming apparatus.

  The invention according to claim 7 is characterized in that at least one of the inner peripheral surface of the magnetic path forming member and the outer peripheral surface of the guide member has an uneven structure for making the line contact or the point contact. Item 7. The image forming apparatus according to Item 6.

According to the first aspect of the present invention, it is possible to shorten the time required to reach the fixing set temperature in the induction heating type fixing device as compared with the case where this configuration is not adopted.
According to invention of Claim 2, compared with the case where this structure is not employ | adopted, the outflow of the heat | fever from a magnetic path formation member to an induction | guidance | derivation member can be suppressed more.
According to invention of Claim 3, compared with the case where this structure is not comprised, the contact area of a magnetic path formation member and a guidance member can be made smaller.
According to the fourth aspect of the present invention, the fixing device can be operated more stably than when the present configuration is not configured.
According to the fifth aspect of the present invention, it is possible to create an induction member that is superior in heat transfer and workability compared to the case where this configuration is not adopted.
According to the sixth aspect of the present invention, the warm-up time can be shortened in the image forming apparatus employing the induction heating type fixing device as compared with the case where this configuration is not employed.
According to the seventh aspect of the present invention, it is possible to more easily realize a state in which the magnetic path forming member and the guide member are in line contact or point contact as compared with the case where this configuration is not adopted.

1 is a diagram illustrating a configuration example of an image forming apparatus to which a fixing device according to an exemplary embodiment is applied. FIG. 2 is a front view illustrating a configuration of a fixing unit of the present embodiment. FIG. 3 is an XX sectional view of the fixing device in FIG. 2. FIG. 3 is a cross-sectional layer configuration diagram of a fixing belt. (a) is a side view of an end cap member, (b) is a top view of the end cap member seen from the Z direction. It is sectional drawing explaining the structure of an IH heater. It is a figure explaining the state of a line of magnetic force (H) in case the temperature of a fixing belt exists in the temperature range below the magnetic permeability change start temperature. (A)-(b) is the figure which demonstrated notionally about the specific example of the uneven structure formed in a temperature-sensitive magnetic member or a guidance member. (A)-(d) is the perspective view which demonstrated the uneven | corrugated structure in more detail. FIG. 6 is a diagram showing the temperature of the fixing belt in relation to time.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
<Description of Image Forming Apparatus>
FIG. 1 is a diagram illustrating a configuration example of an image forming apparatus to which the fixing device of the present embodiment is applied. An image forming apparatus 1 shown in FIG. 1 is a so-called tandem color printer, and includes an image forming unit 10 that forms an image based on image data and a control unit 31 that controls the operation of the entire image forming apparatus 1. Further, for example, a communication unit 32 that receives image data by communicating with a personal computer (PC) 3 or an image reading device (scanner) 4, and a predetermined image for the image data received by the communication unit 32. An image processing unit 33 that performs processing is provided.

The image forming unit 10 includes four image forming units 11Y, 11M, 11C, and 11K (also collectively referred to as “image forming unit 11”), which are examples of toner image forming units arranged in parallel at a predetermined interval. I have. Each image forming unit 11 forms an electrostatic latent image and a photosensitive drum 12 as an example of an image holding body that holds a toner image, and charging that uniformly charges the surface of the photosensitive drum 12 with a predetermined potential. 13, an LED (Light Emitting Diode) print head 14 that exposes the photosensitive drum 12 charged by the charger 13 based on each color image data, and a developer that develops an electrostatic latent image formed on the photosensitive drum 12. 15. A drum cleaner 16 for cleaning the surface of the photosensitive drum 12 after transfer is provided.
Each of the image forming units 11 is configured in substantially the same manner except for the toner stored in the developing device 15, and each forms a toner image of yellow (Y), magenta (M), cyan (C), and black (K). To do.

  The image forming unit 10 also receives the intermediate transfer belt 20 onto which the color toner images formed on the photosensitive drums 12 of the image forming units 11 are transferred, and the color toner images formed on the image forming units 11. A primary transfer roll 21 that sequentially transfers (primary transfer) to the intermediate transfer belt 20 is provided. Further, a secondary transfer roll 22 that batch-transfers (secondary transfer) each color toner image transferred and superimposed on the intermediate transfer belt 20 onto a sheet P that is a recording material (recording paper), and each color toner that is secondarily transferred. A fixing unit 60 is provided as an example of a fixing unit (fixing device) that fixes the image on the paper P. In the image forming apparatus 1 of the present embodiment, the intermediate transfer belt 20, the primary transfer roll 21, and the secondary transfer roll 22 constitute a transfer unit.

  In the image forming apparatus 1 of the present embodiment, under the operation control by the control unit 31, image forming processing is performed by the following process. That is, the image data from the PC 3 or the scanner 4 is received by the communication unit 32, subjected to predetermined image processing by the image processing unit 33, and then sent to each image forming unit 11 as image data for each color. It is done. For example, in the image forming unit 11K that forms a black (K) toner image, the photosensitive drum 12 is uniformly charged at a predetermined potential by the charger 13 while rotating in the arrow A direction, and the image processing unit 33 is charged. The LED print head 14 scans and exposes the photosensitive drum 12 based on the K-color image data transmitted from. As a result, an electrostatic latent image relating to the K color image is formed on the photosensitive drum 12. The K-color electrostatic latent image formed on the photosensitive drum 12 is developed by the developing unit 15, and a K-color toner image is formed on the photosensitive drum 12. Similarly, yellow (Y), magenta (M), and cyan (C) color toner images are formed in the image forming units 11Y, 11M, and 11C, respectively.

  Each color toner image formed on the photosensitive drum 12 of each image forming unit 11 is sequentially electrostatically transferred (primary transfer) onto the intermediate transfer belt 20 that moves in the direction of arrow B by the primary transfer roll 21, and each color toner is superimposed. A superimposed toner image is formed. The superimposed toner image on the intermediate transfer belt 20 is conveyed to a region (secondary transfer portion T) where the secondary transfer roll 22 is disposed as the intermediate transfer belt 20 moves. When the superimposed toner image is conveyed to the secondary transfer unit T, the paper P is supplied from the paper holding unit 40 to the secondary transfer unit T in accordance with the timing. The superimposed toner image is collectively electrostatically transferred (secondary transfer) onto the conveyed paper P by the transfer electric field formed by the secondary transfer roll 22 in the secondary transfer portion T.

Thereafter, the sheet P on which the superimposed toner image is electrostatically transferred is conveyed to the fixing unit 60. The toner image on the paper P conveyed to the fixing unit 60 receives heat and pressure by the fixing unit 60 and is fixed on the paper P. Then, the paper P on which the fixed image is formed is conveyed to a paper stacking unit 45 provided in the discharge unit of the image forming apparatus 1.
On the other hand, the toner (primary transfer residual toner) adhering to the photosensitive drum 12 after the primary transfer and the toner (secondary transfer residual toner) adhering to the intermediate transfer belt 20 after the secondary transfer are respectively drum cleaner 16. , And the belt cleaner 25.
In this way, the image forming process in the image forming apparatus 1 is repeatedly executed for the number of printed sheets.

<Description of fixing unit configuration>
Next, the fixing unit 60 of this embodiment will be described.
2 and 3 are views showing the configuration of the fixing unit 60 of the present embodiment, FIG. 2 is a front view, and FIG. 3 is a sectional view taken along line XX in FIG.
First, as shown in FIG. 3, which is a cross-sectional view, the fixing unit 60 is heated by electromagnetic induction by an IH (Induction Heating) heater 80 and an IH heater 80 as an example of a magnetic field generating member that generates an alternating magnetic field, thereby generating a toner image. A fixing belt 61 as an example of a fixing member to be fixed, a pressure roll 62 disposed so as to face the fixing belt 61, and a pressure pad 63 pressed from the pressure roll 62 via the fixing belt 61 are provided.
Further, the fixing unit 60 includes a holder 65 that supports constituent members such as the pressure pad 63, a temperature-sensitive magnetic member 64 that induces an alternating magnetic field generated by the IH heater 80 to form a magnetic path, and a temperature-sensitive magnetic member 64. A guide member 66 that guides the lines of magnetic force that have passed through, and a peeling assisting member 70 that assists in peeling the paper P from the fixing belt 61.

<Description of fixing belt>
The fixing belt 61 is formed of an endless belt member having an original cylindrical shape. For example, the fixing belt 61 has a diameter of 30 mm and a length in the width direction of 300 mm in the original shape (cylindrical shape). Further, as shown in FIG. 4 (cross-sectional layer configuration diagram of the fixing belt 61), the fixing belt 61 includes a base material layer 611, a conductive heat generating layer 612 laminated on the base material layer 611, and a toner image fixability. The belt member has a multilayer structure including an elastic layer 613 for improving the surface and a surface release layer 614 coated on the uppermost layer.

The base material layer 611 is composed of a heat-resistant sheet-like member that supports the thin conductive heat generating layer 612 and forms the mechanical strength of the fixing belt 61 as a whole. In addition, the base material layer 611 is made of a material having a physical property (relative magnetic permeability, specific resistance) that allows the magnetic field to pass therethrough so that the AC magnetic field generated by the IH heater 80 acts to the temperature-sensitive magnetic member 64, and the thickness. Formed with. On the other hand, the base material layer 611 itself is configured not to generate heat or hardly generate heat due to the action of a magnetic field.
Specifically, as the base material layer 611, for example, a nonmagnetic metal such as nonmagnetic stainless steel having a thickness of 30 to 200 μm (preferably 50 to 150 μm), a resin material having a thickness of 60 to 200 μm, or the like is used.

The conductive heating layer 612 is an example of a conductive layer, and is an electromagnetic induction heating element layer that is electromagnetically heated by an alternating magnetic field generated by the IH heater 80. That is, the conductive heat generating layer 612 is a layer that generates an eddy current when the AC magnetic field from the IH heater 80 passes in the thickness direction.
In general, a general-purpose power source that can be manufactured at low cost is used as a power source for an excitation circuit that supplies an alternating current to the IH heater 80 (see also FIG. 6 below). Therefore, the frequency of the alternating magnetic field generated by the IH heater 80 is generally 20 k to 100 kHz by a general-purpose power source. Thereby, the conductive heat generating layer 612 is configured such that an alternating magnetic field having a frequency of 20 k to 100 kHz enters and passes therethrough.

The region where the alternating magnetic field can enter the conductive heat generating layer 612 is defined as “skin depth (δ)”, which is a region where the alternating magnetic field attenuates to 1 / e, and is derived from the following equation (1). In the equation (1), f is the frequency of the alternating magnetic field (for example, 20 kHz), ρ is the specific resistance (Ω · m), and μr is the relative permeability.
Therefore, the thickness of the conductive heat generating layer 612 is determined by the skin depth (δ) of the conductive heat generating layer 612 defined by the equation (1) such that an alternating magnetic field having a frequency of 20 k to 100 kHz penetrates and passes through the conductive heat generating layer 612. It is configured in a thinner layer. Further, as a material constituting the conductive heat generating layer 612, for example, a metal such as Au, Ag, Al, Cu, Zn, Sn, Pb, Bi, Be, Sb, or a metal alloy thereof is used.

Specifically, as the conductive heating layer 612, a nonmagnetic metal such as Cu having a thickness of 2 to 20 μm and a specific resistance of 2.7 × 10 −8 Ω · m or less (a paramagnetic material having a relative permeability of about 1) is used. Used.
Further, from the viewpoint of shortening the time required for the fixing belt 61 to be heated to the fixing set temperature (hereinafter referred to as “warm-up time”), the conductive heat generating layer 612 is preferably formed as a thin layer.

Next, the elastic layer 613 is composed of a heat-resistant elastic body such as silicone rubber. The toner image held on the sheet P to be fixed is formed by laminating each color toner as powder. Therefore, in order to supply heat uniformly to the entire toner image at the nip portion N, it is preferable that the surface of the fixing belt 61 is deformed following the unevenness of the toner image on the paper P. Therefore, for example, silicone rubber having a thickness of 100 to 600 μm and a hardness of 10 ° to 30 ° (JIS-A) is suitable for the elastic layer 613.
Since the surface release layer 614 is in direct contact with the unfixed toner image held on the paper P, a material having a high release property is used. For example, PFA (tetrafluoroethylene perfluoroalkyl vinyl ether polymer), PTFE (polytetrafluoroethylene), silicone copolymer, or a composite layer thereof is used. If the thickness of the surface release layer 614 is too thin, it is not sufficient in terms of wear resistance, and the life of the fixing belt 61 is shortened. On the other hand, if it is too thick, the heat capacity of the fixing belt 61 becomes too large and the warm-up time becomes long. Therefore, the thickness of the surface release layer 614 is preferably 1 to 50 μm in consideration of the balance between wear resistance and heat capacity.

<Description of pressing pad>
The pressing pad 63 is made of an elastic body such as silicone rubber or fluorine rubber, and is supported by the holder 65 at a position facing the pressure roll 62. Then, it is arranged in a state of being pressed from the pressure roll 62 via the fixing belt 61, and a nip portion N is formed with the pressure roll 62.
The pressing pad 63 includes a pre-nip region 63a on the inlet side of the nip portion N (upstream side in the conveyance direction of the paper P) and a peeling nip region 63b on the outlet side of the nip portion N (downstream side in the conveyance direction of the paper P). Different nip pressures are set. That is, in the pre-nip region 63 a, the surface on the pressure roll 62 side is formed in an arc shape that substantially follows the outer peripheral surface of the pressure roll 62, thereby forming a uniform and wide nip portion N. Further, the peeling nip region 63b is formed so as to be locally pressed from the surface of the pressure roll 62 with a large nip pressure so that the radius of curvature of the fixing belt 61 passing through the peeling nip region 63b becomes small. As a result, a curl (down curl) in a direction away from the surface of the fixing belt 61 is formed on the paper P passing through the peeling nip region 63b to promote the peeling of the paper P from the surface of the fixing belt 61.

  In the present embodiment, the peeling assisting member 70 is disposed on the downstream side of the nip portion N as a peeling assisting means by the pressing pad 63. The peeling auxiliary member 70 is supported by the holder 72 in a state where the peeling baffle 71 is close to the fixing belt 61 in a direction (so-called counter direction) opposite to the rotational movement direction of the fixing belt 61. The curled portion formed on the paper P at the outlet of the pressing pad 63 is supported by the peeling baffle 71, thereby suppressing the paper P from moving toward the fixing belt 61.

<Description of temperature-sensitive magnetic member>
In the present embodiment, the temperature-sensitive magnetic member 64 is formed in an arc shape that follows the inner peripheral surface of the fixing belt 61, and is disposed in contact with the inner peripheral surface of the fixing belt 61. The temperature-sensitive magnetic member 64 is arranged in contact with the fixing belt 61 because the temperature of the temperature-sensitive magnetic member 64 changes corresponding to the temperature of the fixing belt 61, that is, the temperature of the temperature-sensitive magnetic member 64 is changed. This is because the temperature is substantially the same as the temperature 61.

Further, the temperature-sensitive magnetic member 64 has a “permeability change start temperature” (see below), which is a temperature at which the magnetic permeability of the magnetic characteristics changes suddenly, equal to or higher than a fixing set temperature at which each color toner image is melted. The elastic layer 613 and the surface release layer 614 are made of a material set in a temperature range lower than the heat resistant temperature. That is, the temperature-sensitive magnetic member 64 is made of a material having a characteristic (“temperature-sensitive magnetism”) that reversibly changes between ferromagnetic and non-magnetic (paramagnetic) in a temperature range including the fixing set temperature. . The temperature-sensitive magnetic member 64 functions as a magnetic path forming member in a temperature range that is equal to or lower than the permeability change start temperature exhibiting ferromagnetism, and induces magnetic field lines generated by the IH heater 80 and transmitted through the fixing belt 61 to the inside. Thus, a magnetic path of an alternating magnetic field (line of magnetic force) passing through the inside of the temperature-sensitive magnetic member 64 is formed. As a result, the temperature-sensitive magnetic member 64 forms a closed magnetic path that encloses the fixing belt 61 and the exciting coil 82 of the IH heater 80 (see FIG. 6 at a later stage). On the other hand, in the temperature range exceeding the permeability change start temperature, the temperature-sensitive magnetic member 64 crosses the magnetic field lines generated by the IH heater 80 and transmitted through the fixing belt 61 in the thickness direction of the temperature-sensitive magnetic member 64. Make it transparent. Thereby, the magnetic lines of force generated by the IH heater 80 and transmitted through the fixing belt 61 form a magnetic path that passes through the temperature-sensitive magnetic member 64, passes through the inside of the guide member 66, and returns to the IH heater 80.
The “permeability change start temperature” here is a temperature at which the magnetic permeability (for example, the magnetic permeability measured by JIS C2531) starts to decrease continuously. For example, a member such as the temperature-sensitive magnetic member 64 This is the temperature point at which the amount of magnetic flux that passes through (the number of lines of magnetic force) starts to change. Therefore, the permeability change start temperature is a temperature close to the Curie point, which is the temperature at which the magnetism of the substance disappears, but has a concept different from the Curie point.

As a material used for the temperature-sensitive magnetic member 64, a binary magnetic shunt steel such as an Fe—Ni alloy (permalloy) whose permeability change start temperature is set in a range of 140 (fixing set temperature) to 240 ° C., for example. And ternary shunt steels such as Fe—Ni—Cr alloy are used. For example, in the Fe-Ni binary magnetic shunt steel, the permeability change start temperature can be set around 225 ° C. by setting it to about Fe 64% and Ni 36% (atomic ratio). Such metal alloys such as permalloy and magnetic shunt steel are suitable for the temperature-sensitive magnetic member 64 because they are excellent in moldability and workability, have high heat conductivity, and are inexpensive. As other materials, a metal alloy made of Fe, Ni, Si, B, Nb, Cu, Zr, Co, Cr, V, Mn, Mo or the like is used.
Further, the temperature-sensitive magnetic member 64 is formed with a thickness smaller than the skin depth δ (see the above formula (1)) with respect to the AC magnetic field (lines of magnetic force) generated by the IH heater 80. Specifically, for example, when an Fe—Ni alloy is used, the thickness is set to about 50 to 300 μm.

<Description of holder>
The holder 65 that supports the pressing pad 63 is made of a material having high rigidity so that the amount of bending in a state where the pressing pad 63 receives the pressing force from the pressing roll 62 becomes a certain amount or less. Thereby, the uniformity of the pressure in the longitudinal direction (nip pressure N) at the nip portion N is maintained. Furthermore, since the fixing unit 60 according to the present embodiment employs a configuration in which the fixing belt 61 is heated using electromagnetic induction, the holder 65 is made of a material that does not affect or hardly gives influence to the induced magnetic field. It is made of a material that is not affected or hardly affected by the induced magnetic field. For example, a heat-resistant resin such as glass mixed PPS (polyphenylene sulfide) or a paramagnetic metal material such as Al, Cu, or Ag is used.

<Description of induction member>
In the present embodiment, the guide member 66 is formed in an arc shape that follows the inner peripheral surface of the temperature-sensitive magnetic member 64, and is disposed in contact with the inner peripheral surface of the temperature-sensitive magnetic member 64. When the temperature-sensitive magnetic member 64 rises to a temperature equal to or higher than the permeability change start temperature, an AC magnetic field (line of magnetic force) generated by the IH heater 80 is guided to the inside from the conductive heating layer 612 of the fixing belt 61. The eddy current I is easily generated.

The line of magnetic force H after passing through the temperature-sensitive magnetic member 64 reaches the induction member 66 and is induced therein. At this time, the thickness, material, and shape of the guiding member 66 are selected so that the guiding member 66 guides most of the magnetic force lines H from the exciting coil 82 and suppresses leakage of the magnetic force lines H from the fixing unit 60. . Specifically, the induction member 66 may be formed with a thickness (for example, 0.4 mm) sufficiently thicker than the skin depth δ (see the above formula (1)) so that the eddy current I can easily flow. Thereby, even if the eddy current I flows through the induction member 66, the amount of heat generation is also minimized. In the present embodiment, the induction member 66 is made of Al (aluminum) having a substantially circular shape with a thickness of 0.4 mm along the temperature-sensitive magnetic member 64, and is arranged in contact with the inner peripheral surface of the temperature-sensitive magnetic member 64. ing. As other materials, Ag and Cu are suitable.
In addition, the induction member 66 has a function of diffusing the heat generated in the temperature-sensitive magnetic member 64 while guiding the magnetic force lines that have passed through the temperature-sensitive magnetic member 64 as described above. In the present embodiment, since the guide member 66 is in contact with the inner peripheral surface of the temperature-sensitive magnetic member 64, the temperature distribution of the temperature-sensitive magnetic member 64 can be easily made uniform. Further, since the temperature distribution of the temperature-sensitive magnetic member 64 is made uniform, the temperature of the fixing belt 61 is easily made uniform.

<Description of Fixing Belt Drive Mechanism>
Next, a driving mechanism for the fixing belt 61 will be described.
As shown in FIG. 2 which is a front view, the fixing belt 61 is rotated in the circumferential direction while maintaining the cross-sectional shape of both ends of the fixing belt 61 in a circular shape at both axial ends of the holder 65 (see FIG. 3). An end cap member 67 to be driven is fixed. The fixing belt 61 directly receives the rotational driving force from both ends via the end cap member 67, and rotates and moves in the direction of arrow C in FIG. 3 at a process speed of 140 mm / s, for example.
5A is a side view of the end cap member 67, and FIG. 5B is a plan view of the end cap member 67 viewed from the Z direction. As shown in FIG. 5, the end cap member 67 is formed with a fixing portion 67 a fitted inside the both ends of the fixing belt 61 and has an outer diameter larger than that of the fixing portion 67 a, and when the end cap member 67 is attached to the fixing belt 61. Rotating through a flange portion 67d formed so as to project radially from the fixing belt 61, a gear portion 67b to which rotational driving force is transmitted, a support portion 65a formed at both ends of the holder 65, and a coupling member 166. A bearing bearing portion 67c that is freely coupled is provided. Then, as shown in FIG. 2, the support portions 65a at both ends of the holder 65 are fixed to both ends of the casing 69 of the fixing unit 60, whereby the end cap member 67 is coupled to the support portion 65a. It is rotatably supported via the bearing bearing portion 67c.
As a material constituting the end cap member 67, so-called engineering plastics having high mechanical strength and heat resistance are used. For example, phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, LCP resin and the like are suitable.

As shown in FIG. 2, in the fixing unit 60, the rotational driving force from the drive motor 90 is transmitted to the shaft 93 via the transmission gears 91 and 92, and both are transmitted from the transmission gears 94 and 95 coupled to the shaft 93. It is transmitted to the gear portion 67b (see FIG. 5) of the end cap member 67. As a result, a rotational driving force is transmitted from the end cap member 67 to the fixing belt 61, and the end cap member 67 and the fixing belt 61 are integrally rotated.
Thus, the fixing belt 61 rotates by receiving the driving force directly from both ends of the fixing belt 61, so that the fixing belt 61 rotates stably.

Here, when the fixing belt 61 rotates by receiving a driving force directly from the end cap members 67 at both ends, a torque of about 0.1 to 0.5 N · m is generally applied. However, in the fixing belt 61 of the present embodiment, the base material layer 611 is made of, for example, nonmagnetic stainless steel having high mechanical strength. For this reason, even when a torsional torque of about 0.1 to 0.5 N · m acts on the entire fixing belt 61, buckling or the like hardly occurs in the fixing belt 61.
Further, the flange portion 67d of the end cap member 67 suppresses the deviation of the fixing belt 61. In general, the fixing belt 61 at that time is generally 1 to 5 in the axial direction from the end portion (flange portion 67d) side. A compressive force of about 5N works. However, even when the fixing belt 61 receives such a compressive force, since the base material layer 611 of the fixing belt 61 is made of nonmagnetic stainless steel or the like, occurrence of buckling or the like is suppressed.
As described above, the fixing belt 61 according to the present embodiment rotates by receiving a driving force directly from both end portions of the fixing belt 61, and thus stable rotation is performed. At that time, the base material layer 611 of the fixing belt 61 is made of, for example, non-magnetic stainless steel having high mechanical strength, thereby realizing a structure in which buckling or the like hardly occurs against torsion torque or compression force. is doing. Furthermore, since the base material layer 611 and the conductive heat generating layer 612 are formed as thin layers to ensure the flexibility and flexibility of the fixing belt 61 as a whole, deformation and shape restoration following the nip portion N are prevented. Done.

Returning to FIG. 3, the pressure roll 62 is arranged so as to face the fixing belt 61, and rotates in the direction of arrow D in FIG. 3 at a process speed of 140 mm / s, for example, following the fixing belt 61. Then, a nip portion N is formed in a state where the fixing belt 61 is sandwiched between the pressure roll 62 and the pressing pad 63, and the sheet P holding the unfixed toner image is passed through the nip portion N, so that the heat and pressure To fix the unfixed toner image on the paper P.
The pressure roll 62 includes, for example, a solid aluminum core (cylindrical metal core) 621 having a diameter of 18 mm, and a heat-resistant elastic body layer 622 such as a silicone sponge having a thickness of 5 mm, which is coated on the outer peripheral surface of the core 621. Further, for example, a release layer 623 made of a heat-resistant resin coating such as PFA containing carbon having a thickness of 50 μm or a heat-resistant rubber coating is laminated. Then, the pressing pad 63 is pressed through the fixing belt 61 with a load of 25 kgf, for example, by a pressing spring 68 (see FIG. 2).

<Description of IH heater>
Next, the IH heater 80 that performs electromagnetic induction heating by applying an AC magnetic field to the conductive heat generating layer 612 of the fixing belt 61 will be described.
FIG. 6 is a cross-sectional view illustrating the configuration of the IH heater 80 of the present embodiment. As shown in FIG. 6, the IH heater 80 includes a support 81 made of a nonmagnetic material such as a heat resistant resin, and an exciting coil 82 that generates an alternating magnetic field. Further, an elastic support member 83 made of an elastic body that fixes the excitation coil 82 on the support 81 and a magnetic core 84 that forms a magnetic path of an alternating magnetic field generated by the excitation coil 82 are provided. Furthermore, a shield 85 that shields the magnetic field, a pressure member 86 that pressurizes the magnetic core 84 toward the support 81, and an excitation circuit 88 that supplies an alternating current to the excitation coil 82 are provided.

The support 81 is formed in a shape whose cross section is curved along the surface shape of the fixing belt 61, and an upper surface (supporting surface) 81 a that supports the exciting coil 82 has a predetermined gap (for example, 0) from the surface of the fixing belt 61. 0.5 to 2 mm). Moreover, as a material which comprises the support body 81, heat resistance, such as heat resistant resins, such as heat resistant glass, a polycarbonate, polyether sulfone, PPS (polyphenylene sulfide), or the glass fiber mixed with these, for example. Some non-magnetic materials are used.
The exciting coil 82 is configured by winding, for example, 90 litz wires, which are bundled with, for example, 90 copper wires having a diameter of 0.17 mm and wound in a closed loop with a hollow shape such as an ellipse, an ellipse, or a rectangle. . Then, when an alternating current having a predetermined frequency is supplied to the exciting coil 82 from the exciting circuit 88, an alternating magnetic field centered around a litz wire wound in a closed loop is generated around the exciting coil 82. . Generally, the frequency of the alternating current supplied from the excitation circuit 88 to the excitation coil 82 is 20 k to 100 kHz generated by the general-purpose power source.

The magnetic core 84 is made of, for example, a ferromagnetic material made of an oxide or alloy material having a high magnetic permeability such as soft ferrite, ferrite resin, amorphous alloy (amorphous alloy), permalloy, and magnetic shunt steel. It functions as a forming means. The magnetic core 84 induces a magnetic force line (magnetic flux) generated by the alternating magnetic field generated by the exciting coil 82, and crosses the fixing belt 61 from the magnetic core 84 toward the temperature-sensitive magnetic member 64. A path of magnetic lines of force (magnetic path) is formed so as to pass through and return to the magnetic core 84. That is, the AC magnetic field generated by the excitation coil 82 is configured to pass through the inside of the magnetic core 84 and the inside of the temperature-sensitive magnetic member 64 so that the magnetic lines of force wrap the fixing belt 61 and the excitation coil 82 inside. A closed magnetic circuit is formed. As a result, the magnetic field lines of the alternating magnetic field generated by the exciting coil 82 are concentrated in a region facing the magnetic core 84 of the fixing belt 61.
Here, the magnetic core 84 is preferably made of a material having a small loss due to magnetic path formation. Specifically, the magnetic core 84 is desirably used in a form that reduces the eddy current loss (current path interruption or division by slits, thin plate bundling, etc.), and is preferably formed of a material having a small hysteresis loss.
Further, the length of the magnetic core 84 along the rotation direction of the fixing belt 61 is configured to be smaller than the length of the temperature-sensitive magnetic member 64 along the rotation direction of the fixing belt 61. Thereby, the leakage of magnetic lines of force to the periphery of the IH heater 80 is reduced, and the power factor is improved. Furthermore, electromagnetic induction to the metal member constituting the fixing unit is suppressed, and the heat generation efficiency in the fixing belt 61 (conductive heat generation layer 612) is increased.

<Description of the state in which the fixing belt generates heat>
Subsequently, a state in which the fixing belt 61 generates heat by the alternating magnetic field generated by the IH heater 80 will be described.
First, as described above, the permeability change start temperature of the temperature-sensitive magnetic member 64 is within a temperature range that is not less than the set fixing temperature for fixing each color toner image and not more than the heat resistance temperature of the fixing belt 61 (for example, 140 to 240 ° C.). When the temperature of the fixing belt 61 is equal to or lower than the magnetic permeability change start temperature, the temperature of the temperature-sensitive magnetic member 64 adjacent to the fixing belt 61 is also started corresponding to the temperature of the fixing belt 61. Below temperature. Therefore, since the temperature-sensitive magnetic member 64 exhibits ferromagnetism, the magnetic field lines H of the alternating magnetic field generated by the IH heater 80 pass through the fixing belt 61 and then pass through the inside of the temperature-sensitive magnetic member 64 along the spreading direction. To form a magnetic path. Here, the “spreading direction” means a direction orthogonal to the thickness direction of the temperature-sensitive magnetic member 64.

  FIG. 7 is a diagram for explaining the state of the lines of magnetic force (H) when the temperature of the fixing belt 61 is in the temperature range equal to or lower than the permeability change start temperature. As shown in FIG. 7, when the temperature of the fixing belt 61 is in a temperature range equal to or lower than the permeability change start temperature, the magnetic field lines H of the alternating magnetic field generated by the IH heater 80 are transmitted through the fixing belt 61. A magnetic path passing through the inside of the temperature-sensitive magnetic member 64 along the spreading direction (direction orthogonal to the thickness direction) is formed. Therefore, the number of magnetic field lines H (magnetic flux density) per unit area in the region crossing the conductive heat generating layer 612 of the fixing belt 61 increases.

  That is, after the magnetic field lines H are radiated from the magnetic core 84 of the IH heater 80 and pass through the regions R1 and R2 across the conductive heat generating layer 612 of the fixing belt 61, the magnetic field lines H enter the inside of the temperature-sensitive magnetic member 64 which is a ferromagnetic material. Be guided. Therefore, the magnetic field lines H crossing the conductive heat generating layer 612 of the fixing belt 61 in the thickness direction are concentrated so as to enter the inside of the temperature-sensitive magnetic member 64, and the magnetic flux density in the regions R1 and R2 increases. Further, even when the magnetic field lines H that have passed through the inside of the temperature-sensitive magnetic member 64 along the spreading direction return to the magnetic core 84 again, in the region R3 that crosses the conductive heating layer 612 in the thickness direction, the magnetic field in the temperature-sensitive magnetic member 64 is increased. It is concentrated toward the magnetic core 84 from the lower part. Therefore, the magnetic force lines H that cross the conductive heat generating layer 612 of the fixing belt 61 in the thickness direction are concentrated from the temperature-sensitive magnetic member 64 toward the magnetic core 84, and the magnetic flux density in the region R3 is also increased.

In the conductive heating layer 612 of the fixing belt 61 where the magnetic lines H cross in the thickness direction, an eddy current I proportional to the amount of change in the number of magnetic lines H per unit area (magnetic flux density) is generated. Thereby, as shown in FIG. 7, a large eddy current I is generated in the regions R1, R2 and R3 where the amount of change in magnetic flux density is large. The eddy current I generated in the conductive heat generating layer 612 generates Joule heat W (W = I2R), which is the product of the specific resistance value R of the conductive heat generating layer 612 and the square of the eddy current I. Thereby, a large Joule heat W is generated in the conductive heat generating layer 612 where the large eddy current I is generated.
As described above, when the temperature of the fixing belt 61 is in the temperature range equal to or lower than the permeability change start temperature, large heat is generated in the regions R1 and R2 and the region R3 where the lines of magnetic force H cross the conductive heat generating layer 612. Thereby, the fixing belt 61 is heated.

  Incidentally, in the fixing unit 60 of the present embodiment, the temperature-sensitive magnetic member 64 is disposed in contact with the fixing belt 61 on the inner peripheral surface side of the fixing belt 61. As a result, the magnetic core 84 that guides the magnetic force lines H generated by the exciting coil 82 to the inside and the temperature-sensitive magnetic member 64 that guides the magnetic force lines H transmitted through the fixing belt 61 in the thickness direction are close to each other. The configuration is realized. For this reason, the AC magnetic field generated by the IH heater 80 (excitation coil 82) forms a loop with a short magnetic path, so that the magnetic flux density and the magnetic coupling degree in the magnetic path increase. Accordingly, when the temperature of the fixing belt 61 is in a temperature range equal to or lower than the magnetic permeability change start temperature, heat is more efficiently generated in the fixing belt 61.

  Further, since the temperature-sensitive magnetic member 64 is a ferromagnetic material in a temperature range below the permeability change start temperature, it self-heats due to the magnetic field lines H. Here, the fixing belt 61 is deprived of heat by performing fixing, and thus its temperature is lowered. However, the fixing belt 61 is reheated by the heat generated by the temperature-sensitive magnetic member 64 together with the heat generated by the fixing belt 61. be able to. Therefore, it is possible to quickly raise the temperature of the fixing belt 61 to the fixing set temperature.

  However, in the present embodiment, as described above, the temperature distribution of the temperature-sensitive magnetic member 64 is made uniform, and the temperature of the fixing belt 61 is also made uniform, so that the fixing belt 61, the temperature-sensitive magnetic member 64, and the induction are guided. The members 66 are arranged in contact with each other. Therefore, the heat generated by the temperature-sensitive magnetic member 64 not only flows into the fixing belt 61 but also flows into the guide member 66. Therefore, in particular, when the main switch of the image forming apparatus 1 (see FIG. 1) is turned on and the fixing belt 61 is heated to the fixing set temperature, the induction member 66 is deprived of heat, and the temperature of the fixing belt 61 is increased. Decreases. As a result, there is a problem that the warm-up time tends to be long.

Therefore, in this embodiment, this problem is solved by forming an uneven structure on at least one of the inner peripheral surface of the temperature-sensitive magnetic member 64 and the outer peripheral surface of the guide member 66.
That is, by forming an uneven structure on at least one of the inner peripheral surface of the temperature-sensitive magnetic member 64 and the outer peripheral surface of the induction member 66, the contact area between the temperature-sensitive magnetic member 64 and the induction member 66 is reduced. Thereby, particularly when the main switch of the image forming apparatus 1 is turned on, the heat generated by the temperature-sensitive magnetic member 64 can be prevented from flowing into the induction member 66. As a result, it is possible to suppress a decrease in the temperature increase rate of the fixing belt 61.

Hereinafter, the uneven structure will be described in more detail.
8A and 8B are diagrams conceptually illustrating specific examples of the uneven structure formed on the inner peripheral surface of the temperature-sensitive magnetic member 64 and the outer peripheral surface of the guide member 66. FIG. Hereinafter, the description will be made on the assumption that the temperature-sensitive magnetic member 64 has an uneven structure.

Here, the example shown in FIG. 8A is an example in which a recess having a groove shape is used to form an uneven structure on the temperature-sensitive magnetic member 64a. Further, the example shown in FIG. 8B is an example in which a circular convex portion as viewed from above is used to form a concave-convex structure on the temperature-sensitive magnetic member 64b.
In FIG. 8A, the groove shape is formed in parallel with each other along the rotation direction of the fixing belt 61. By forming such an uneven structure on the temperature-sensitive magnetic member 64a, the temperature-sensitive magnetic member 64 and the guide member 66 are in line contact, and thus the contact area can be reduced. As a result, the heat capacity of the induction member 66 can be substantially reduced, so that the heat generated by the temperature-sensitive magnetic member 64a can be suppressed from flowing out to the induction member 66. The direction in which the groove shape is provided is not particularly limited, and may be, for example, a direction perpendicular to the rotation direction of the fixing belt 61 or an oblique direction. Furthermore, it does not need to be provided at equal intervals, and may be provided at irregular intervals.

Further, in the example shown in FIG. 8B, the temperature-sensitive magnetic member 64b and the induction member 66 are in point contact with each other because a circular convex portion as viewed from above is used to form the concavo-convex structure. become. Therefore, as in the case described with reference to FIG. 8A, the contact area can be reduced, so that the heat generated in the temperature-sensitive magnetic member 64 b can be prevented from flowing out to the induction member 66.
In the example shown here, the convex portions are not particularly regular. However, it may have predetermined regularity. For example, it can be arranged in a lattice or zigzag pattern.

FIGS. 9A to 9D are perspective views illustrating the above-described uneven structure in more detail.
And the example shown to Fig.9 (a) is the elements on larger scale which expanded the uneven structure of the temperature-sensitive magnetic member 64a shown in Fig.8 (a), The example shown in FIG.9 (b) is It is the elements on larger scale which expanded the uneven structure of the temperature-sensitive magnetic member 64b shown in FIG.8 (b).
As shown in FIG. 9A, a concave-convex structure as shown in FIG. 8A is formed by forming a concave portion 641 having a square cross section as a groove shape. By forming such a concavo-convex structure on the temperature-sensitive magnetic member 64a, the temperature-sensitive magnetic member 64a and the induction member 66 are in line contact with each other, so that the contact area can be reduced.

Here, the shape of the cross section is not particularly limited, and for example, concave portions such as a V shape, a U shape, a semicircular shape, and a spindle shape can be used. Moreover, it is not restricted to a recessed part, You may provide a convex part substantially parallel to each other. An uneven structure can be formed by using this protrusion. Furthermore, it is good also as a hook shape and a waveform shape by making a recessed part adjoin.
FIG. 9C shows an example in which a ridge shape is used to form a concavo-convex structure on the temperature-sensitive magnetic member 64c. The collar 643 shown in FIG. 9C can reduce the contact area with the induction member 66 in the same manner as described for the temperature-sensitive magnetic member 64a.

  Further, in the example shown in FIG. 9B, the concavo-convex structure shown in FIG. 8B is formed by forming the hemispherical convex portion 642. By forming such a concavo-convex structure on the temperature-sensitive magnetic member 64b, the temperature-sensitive magnetic member 64b and the induction member 66 are in point contact, so that the contact area can be reduced.

The shape of the convex portion is not particularly limited, and various shapes such as a cylindrical shape, a pyramid shape, and a spindle shape can be used. Furthermore, these shapes may be mixed. Moreover, not a convex part but a recessed part can also be utilized.
FIG. 9D shows an example in which a cylindrical recess is used to form an uneven structure on the temperature-sensitive magnetic member 64d. By providing the recess 644, the contact area with the induction member 66 can be reduced as described in the case of the temperature-sensitive magnetic member 64b. FIG. 9D shows an example in which the recesses 644 are regularly arranged in a lattice pattern.

  The contact area between the temperature-sensitive magnetic member 64 and the guide member 66 can be adjusted by the concavo-convex structure described in detail above. That is, the contact area is changed by changing the groove shape, the number of protrusions and the number of recesses, and the interval. Therefore, it is possible to set the optimum contact area in consideration of both the soaking effect due to the thermal diffusion caused by providing the guide member 66 and the effect of shortening the warm-up time. In other words, after the warm-up time is finished, the fixing unit 60 actually performs the fixing operation. During operation of the fixing unit 60, it is important to form a concavo-convex structure so that the correspondence between the temperature of the fixing belt 61 and the temperature of the temperature-sensitive magnetic member 64 is maintained. As a result, the fixing unit 60 can be operated more stably. In order to suppress the outflow of heat from the temperature-sensitive magnetic member 64 to the induction member 66, a method of arranging the temperature-sensitive magnetic member 64 and the induction member 66 apart from each other can be considered. In this case, the setting of this distance is finely defined. There is a need to. Therefore, there arises a problem that design and assembly become difficult. On the other hand, in the present embodiment, there is no problem that it becomes difficult to design and assemble by providing the concavo-convex structure. Therefore, in this respect as well, the method of suppressing the outflow of heat from the temperature-sensitive magnetic member 64 to the induction member 66 by forming an uneven structure on the temperature-sensitive magnetic member 64 and the induction member 66 according to the present embodiment is excellent.

  The concavo-convex structure described above can be formed by a normal method such as machining or etching. In addition, when forming the uneven structure mentioned above in the direction of the induction | guidance | derivation member 66, it is preferable to use the member whose heat conductivity is higher than a magnetic path formation member as a material. An example of such a material is Al (aluminum). The use of Al (aluminum) is also preferable from the viewpoint of excellent workability.

Example 1
The fixing unit 60 shown in FIGS. 2 and 3 was used as the fixing device, and the temperature-sensitive magnetic member 64a shown in FIGS. 8A and 9A was used as the temperature-sensitive magnetic member. Here, the quadrangular grooves were formed on the fixing belt 61 by machining in parallel with the rotation direction to create a concavo-convex structure. The groove width at this time was 2 mm, and the interval between the substantially parallel grooves was 2 mm at equal intervals. Under this condition, the fixing unit 60 was started and the relationship between the time and temperature of the fixing belt 61 was measured.

(Comparative Example 1)
The fixing unit 60 was started in the same manner as in Example 1 except that a temperature-sensitive magnetic member having no uneven structure as shown in Example 1 was used, and the relationship between the time and temperature of the fixing belt 61 was measured. .

  The results are shown in FIG. FIG. 10 is a diagram showing the temperature of the fixing belt 61 in relation to time. Here, the horizontal axis represents time as a unit (s), and the vertical axis represents the temperature of the fixing belt 61 as a unit (° C.). As can be seen from FIG. 10, when the temperature-sensitive magnetic member 64a having the concavo-convex structure of Example 1 is used, the fixing unit 60 is started and the fixing set temperature is reached in 17 seconds. On the other hand, when the temperature-sensitive magnetic member having no uneven structure of Comparative Example 1 is used, the fixing set temperature is reached in 27 seconds. Therefore, it can be seen that the heating rate of the fixing belt 61 is faster in the first embodiment than in the first comparative example, and reaches the predetermined fixing set temperature in a shorter time. That is, the warm-up time is shortened. Further, when the fixing unit 60 of the first embodiment is used for operation, the temperature distribution of the fixing belt 61 is not changed as compared with the first comparative example, and the temperature uniformity of the fixing belt 61 is affected. There was no.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 60 ... Fixing unit, 61 ... Fixing belt, 62 ... Pressure roll, 64, 64a, 64b, 64c, 64d ... Temperature-sensitive magnetic member, 66 ... Induction member, 80 ... IH heater, 82 ... Excitation Coil, 84 ... magnetic core, 611 ... base material layer, 612 ... conductive heating layer

Claims (7)

A fixing member having a conductive layer and fixing the toner to the recording material by electromagnetic induction heating of the conductive layer;
A magnetic field generating member that generates an alternating magnetic field that intersects the conductive layer of the fixing member;
Formed in contact with the inner peripheral surface of the fixing member to form a magnetic path of an alternating magnetic field generated by the magnetic field generating member and to conduct heat to the fixing member by electromagnetic induction heating Members,
An inductive member that is disposed in contact with the inner peripheral surface of the magnetic path forming member, induces magnetic lines of force that have passed through the magnetic path forming member, and diffuses heat generated in the magnetic path forming member;
With
A fixing device having an uneven structure on at least one of an inner peripheral surface of the magnetic path forming member and an outer peripheral surface of the guide member.   The fixing device according to claim 1, wherein the concavo-convex structure is formed in a groove shape or a ridge shape arranged substantially parallel to each other.   The fixing device according to claim 1, wherein the concavo-convex structure is formed by a convex portion or a concave portion having at least one shape selected from a hemispherical shape, a cylindrical shape, a pyramid shape, and a spindle shape.   The fixing device according to claim 1, wherein the uneven structure is formed so that a correspondence relationship between a temperature of the fixing member and a temperature of the magnetic path forming member is maintained.   The fixing device according to claim 1, wherein the guide member is made of a member having a higher thermal conductivity than the magnetic path forming member. Toner image forming means for forming a toner image;
Transfer means for transferring the toner image formed by the toner image forming means onto a recording material;
Fixing means for fixing the toner image transferred onto the recording material to the recording material;
The fixing means is
A fixing member having a conductive layer and fixing the toner to the recording material by electromagnetic induction heating of the conductive layer;
A magnetic field generating member that generates an alternating magnetic field that intersects the conductive layer of the fixing member;
A magnetic path forming member that is arranged in contact with the inner peripheral surface of the fixing member to form a magnetic path of an alternating magnetic field generated by the magnetic field generating member and conducts heat to the fixing member by electromagnetic induction heating. When,
An induction member that is arranged in line contact or point contact with the inner peripheral surface of the magnetic path forming member and that induces magnetic lines of force that have passed through the magnetic path forming member and diffuses heat generated in the magnetic path forming member; ,
An image forming apparatus comprising:   The image forming apparatus according to claim 6, wherein at least one of an inner peripheral surface of the magnetic path forming member and an outer peripheral surface of the guide member has an uneven structure for making the line contact or the point contact.

Images